Replace 10.10.0.1 with the IP address of your pfSense LAN. If you get an access error then you need to add your LAN IP & localhost to squid's External Cache Managers config under Local Cache - Squid Cache General Settings like this:

Like I said earlier, if you have a large cache structure that is mostly full on a slower hard disk then you will have elevated Cache Miss times. The longer it takes to search the cache before declaring a MISS, the worse your numbers will be.